Vapor coating employing degassing of coating metal



Oct. 29, 1968 l.. 1 Asi-:BURN ETAL VAPOR COATING EMPLOYING DEGASSING OFCOATING METAL Filed June 25, 1964 M W M P d d l S N E m f 5% 0 3, 2 WCWLO FV W MKM United States Patent O 3,408,224 VAPGR COATING EMPLOYINGDEGASSING OF COATING METAL Lennie L. Ashburn, Rockledge, and Charles L.Starbuck, Valley Forge, Pa., assgnors to Pennsalt Chemicals Corporation,Philadelphia, Pa., a corporation of Pennsylvania Filed June 25, 1964,Ser. No. 378,021 14 Claims. (Cl. 117-107) ABSTRACT F THE DISCLOSURE Anapparatus and method for vapor coating metallic materials on a substratewherein the material to be coated on the substrate is melted outside anevacuated coating chamber, and then conveyed to a vessel within thechamber for vaporization.

This invention relates to a vapor coating apparatus and method, and moreparticularly, to apparatus and method for vapor deposition of metalliccoating materials on a substrate.

Vaporization of coating material within a-n evacuated chamber andcondensation of the vapors on a substrate has been proposed heretofore.Such structure is fairly well known to those skilled in the art andgenerally provides for introduction of coating material to a boatdisposed within the evacuated chamber. The coating material is generallyvaporized within the boat.

An improvement over such known devices is set forth in copendingapplication Ser. No. 313,658, now abandoned, filed on Oct. 3, 1963, andentitled Vapor Coating Apparatus and Method. In said application, it ispointed out that numerous advantages are attained when the material tobe coated is rendered 'molten in a vessel outside of the evacuatedchamber and then conveyed to the boat within the chamber. The presentinvention likewise utilizes a vessel for the coating material disposedoutside of the evacuated chamber. Prior to conveying the coatingmaterial into the evacuated chamber for directing vaporized coatingmaterial toward a substrate, the coating material is degassed. Thecoating material may be metallic material such as zinc, tin, aluminum,etc. or may be non-metallic in nature. Coating material, especiallymetal, generally has gases therewithin which should be removed beforethe coating material is vaporized.

When the coating material has not been degassed prior to beingvaporized, the release of the gases during the vaporization of thecoating material under vacuum results in small bursts. These smallbursts often result in the coating material being splashed on theenvironment surrounding the boat or other vapor directing means disposedwithin the evacuated chamber. By degassing the coating material prior todirecting the same into the evacuated coating chamber, theabove-mentioned bursts are eliminated and thereby render the coatingaction more uniform. As a result thereof, higher speeds may be attainedfor the substrate to be coated.

It is an object of the present invention to provide a novel vaporcoating apparatus.

It is another object of the present invention to provide a novel vaporcoating method.

It is another object of the present invention to degas the coatingmaterial before it is vaporized and directed toward a substrate.

It is another object of the present invention to provide a vapor coatingapparatus and method which eliminates the problem of gas burstsresulting from gas dissolved in the molten coating material to becondensed on a substrate.

"ice

It is another object of the present invention to provide a coatingapparatus and method wherein degassed vaporized coating material isconveyed to an evacuated coating chamber for condensation o'n asubstrate.

Other objects will appear hereinafter.

For the purposes of illustrating the invention, there are shown in thedrawings forms which are presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIGURE 1 is a diagrammatic sectional view of one embodiment of thepresent invention.

FIGURE 2 is a partial view of apparatus similar to FIGURE 1 but directedto another embodiment of the present invention.

FIGURE 3 is a diagrammatic sectional view of another embodiment of thepresent invention.

Referring to the drawi-ng in detail, wherein like numetals indicate likeelements, there is shown in FIGURE 1 a diagrammatic illustration of oneembodiment of the present invention wherein the apparatus is designatedgenerally as 1t).

The apparatus 10 comprises a coating housing 12 having substrate guidemeans such as driven roller 14 disposed therewithin. Roller 14 is drivenby a motor 16. Disposed within the housing 12 there is provided a boat18 having heating coils associated therewith. A pump 20 is provided forevacuating the interior of the housing 12. A substrate 22 is adapted tobe unwound from a reel within the housing 12 and wound around the roller14. Substrate 22 may be a strip of metal, paper, polymeric resin, etc.Alternatively, the substrate 22 may enter the housing 12 through a sealin one wall and exit through a seal in another wall of the housing 12.

A conduit 24 enters the housing 12 and is in communication at one endwith the interior of the boat 18. Conduit 24 may be provided, externallyof the housing 12, with a control valve 26 and a coupling 28. Whencomplete advantage of the full barometric leg height is taken, valve 26may be eliminated. The other end of the conduit 24 communicates with theinterior of a vacuum chamber 30. Chamber 30 is adapted to be evacuatedby a pump 32 which communicates with the housing 30 at a point disposedto one side of a baille 34. To minimize loss of vapors and prevent vaporentrainment in the pumping system, a sutiable condenser 33 may beprovided between pump 32 and chamber 30. An inlet leg 38 communicateswith the housing 30 on the opposite side of the baille 34. A oor 36 inthe housing 3) may slope from the point where the inlet leg 38communicates therewith to the point where the conduit 24 communicatestherewith. Any suitable structure or orientation may be provided todrain molten metal from conduit 24 and/or chamber 30 when the apparatus10 is to be shut down for a period of time after operation of the same.

The `leg 38 Iextends downwardly into the molten coating material 42disposed within a vessel 40. The coating material 42 may be rendered andmaintained in a molten state by means of a heater 44 disposed below thevessel 40. The coating material may be metallic in nature such as zinc,tin, etc. Alternatively, the coating material 42 may be a non-metallicmaterial such as a polymeric resin, photography emulsions, etc.

The level of the molten coating material 42 may be automaticallycontrolled within a predetermined range or an alarm system may beprovided to give an indication that the level of the coating material 42has fallen below a predetermined level. Such alarm system may include aoat 46 having a contact actuator 50. The float and its actuator may beguided for vertical movement by a bracket 48 coupled to the vessel 40.When the level of the coating material 42 falls below a predeterminedlevel, the contact actuator-50 .will close vswitch v52.therebycompleting Yacircuit from the battery 54 to the alarm 56. The alarm 56may be visible or audible thereby signalling the need for introductionof more coating material into thervessel 40. It will be appreciated thatother types of liquid level alarm systems may be provided. For example,spaced electrodes may be utilized in the coating material 42 with analarm being given when the uppermost electrode is exposed;

The operation of the apparatus is as follows:

The coating material 42 disposed within the vessel 40 will be exposed toatmosphere. Hence, removal. of slag from the surface vof the coatingmaterial may -be accomplished without interfering with the continuouscoating action on the substrate 22. Vacuum pump 32 draws molten coatingmaterial 42 into the housing 30. The coating material is then exposed toan evacuated atmosphere which removesgases from the coating material asthe coating material flows along the bottom wall 36 of the housing 30.Thereafter, the degassed coating material is conveyed to the boat 18wherein it is evaporated and condensed on the substrate 22. Due to thepressure differentials, the housing 30 and vessel 40 may be disposedbe,- low the level of the coating materialwithin theboat 18. Theconveying of coating material may be assisted by utilizing gravitywhereby housing 30 may be higher than the boat 18. The pressuredifferential will decrease as the level of the coating material 42decreases within vessel 40.

When the level of the coating material 42 falls below a predeterminedlevel, float 46 will descend therewith until contact actuator 50 closesswitch 52. Thereafter, alarm 56 will alert operators to the fact thatmore coating material must be introduced into vessel 40. The heater 44will render the coating material molten and maintain the coatingmaterial in a molten state within the vessel 40, Adjustment of valve 26may be utilized to vary the ow rate of coating material. In order toprevent undue cooling of the coating material, conduit 24 may beinsulated and/or provided with electrical heaters as desired.

In FIG. 2, there is illustrated an apparatus designated generally as 60.Apparatus 60 is identical with apparatus 10 except as willbe describedhereinafter.

'Coating material 75 is rendered molten and maintained in a molten statein vessel 72 by a heater 74. A vacuum chamber 62 is supported in anyconvenient manner above the vessel 72. Chamber 62 has an inlet leg 68and an outlet leg 70 each of which communicate with the molten material75 below the surface level thereof. A batie 66 is provided within thehousing 62 opposite the portion wherein leg 68 communicates with chamber62.

On opposite side of the bafe 66, a vacuum pump 64 communicates with ltheinterior of vacuum chamber 62. Circulation of coating material 75 up leg68, through chamber 62, and down leg 70 may be accomplished in anyconvenient manner. Circulation can be made more positive by a gas liftmeans or by an induction pumping coil inducing an alternating ilux inone or both legs. An alarm system may be provided as described above.

The apparatus 60 operates in the same manner as described above. Thecoating material 75 will be continuously recirculated into the chamber62 wherein the coating material will be degassed and then returned tothe vessel 72. From the vessel 72, the degassed coating material 75 willbe conveyed by way of conduits 76 and 24 to the boat 18. In view of theabove description of apparatus 10, further description of apparatus 60is not deemed necessary.

In FIGURE 3, there is illustrated another embodiment of the presentinvention designated generally as 80. The

apparatus 80 is generally similar to the embodiments de-v scribed abovein that coating material will be degassed before it is introduced intothe evacuated coating chamber. Thus, coating material 86 is renderedand/or maintained in a molten state within vessel 82 by heater 84. Avacuum chamber 88 is supported in any convenient manner above the vessel82. An inlet leg 91 communir-catesf-'at oneendwith the interior ofAvacuumchamber 88. The other end of leg 91 is disposed below the surfacelevel of the coating material 86.

Vacuum chamber 88 is adapted to be evacuated by pump 90. A batiie isdisposed between the pump 90 and the yinlet leg 91. The coating material86 is degassed withinthe vacuum chamber 88 and'then ows below a weir'92",fthro'ugh conduit "93 into'boiler 94.,The degassedcoating'mater-iaiisl then vaporized withinVv boiler 9.4 and dischargesfrom the same in a lvaporized or'superheated state through conduit 95having a control valve 96 therein. Conduit 95 communicates Withamanifold 97 having a plurality of discharge nozzles 98, each of whichmay be heated to further superheat the coating material 86. The manifold97 is disposed, within an evacuated housing 100 having a coating chambertherewith. A roller 104 within the housingf100 is driven by a motor 102and guides the substrate 99 which passes or moves over the nozzles 98.

The apparatus enables the thickness and pattern of the coating materialcondensed on the substrate 99 to be controlled very accurately. Thus,very thin layers of coating material may be accurately condensed on thesubstrate 99 due tothe fact that the coating material is vaporizedoutside of the coating chamber and discharged lby'nozzles 98 which areof the type which discharge the vaporized coating material in the formof a mist. Also, when the coating material 86 is a metal such as zinc,the slag will remain within the vessel 82. Thus, the annoying problem ofslag within the coating chamber is avoided by thestructural'interrelationship of apparatus 80. Thus, apparatus 80 enablesa substrate to be coated uniformly at high rates of speed.

In each of the embodiments described above, the coating material isrendered molten and/or heated within the outside vessel, then degassed,and then conveyed to means within the coating chamber for directingvaporized coating material at the substrate. As pertains to apparatus 10vand 60, the delivery of preheated coating -material to the boat 18reduces the thermal shock thereon and enables the boat 18 to be madesmaller and of cheaper materials.

It is within the scope of the invention to convey the molten coatingmaterial to chamber 30 or 88 by a means other than a barometric leg.Thus, the coating material could be conveyed to said chambers by gravityor positive pumping with suitable valves or the like to control tlow.

The present invention may be embodied in other specie forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification asindicating the scope of theinvention.

We claim:

1. A coating method comprising the steps of heating metalin a vesselexposing, to a temperature above its melting point, the melted metal tovacuum in a first evacuated housing until the molten metal is degassed,moving the degassed molten metal to a second evacuated housing,vaporizing the degassed molten metal in said second housing, moving asubstrate in `said second housing and condensing the vaporized degassedmolten metal on said substrate within said second housing.

2. A coating method comprising the steps of melting a metal in.aIvessel,. introducing heat into the metal to maintain the same in amolten state, moving the metal in a molten state through anair-evacuated chamber until the molten metal is degassed, thenvaporizing the degassed molten metal, after transference to a secondevacuated chamber and condensing the vaporized degassed metal on asubstrate which is disposed within the second evacuated chamber.

3. A method in accordance with claim 2 including the step y.of sensingthe level of molten metal in said vessel, and generating a signal whenthe level of the metal falls below a predetermined point.

4. A method in accordance with claim 2 wherein the step of vaporizingthe metal is accomplished by discharging the vaporized degassed metalthrough nozzles directed toward the substrate.

5. A method in accordance with claim 2 wherein said step of degassingthe metal includes withdrawing molten metal from the vessel andreturning degassed molten metal to said vessel.

v6. Apparatus comprising a housing having a coating chamber, means forsupporting a substrate in said chamber, means for evacuating saidchamber, means within said chamber for directing vaporized coatingmaterial at the substrate, a vessel outside said chamber and in com--munication with said vapor directing means, said vessel being adaptedto support molten coating material therewithin, and means for degassingthe coating material before the coating material is conveyed to saidvapor directing means.

7. Apparatus in accordance with claim 6 wherein said vapor degassingmeans has an inlet leg extending into said vessel.

8. Apparatus in accordance with claim 7 wherein said degassing meansincludes a vacuum chamber, and means for evacuating said vacuum chamber.

9. Apparatus in accordance with claim 6 including liquid levelresponsive means associated with said vessel for generating a Signal asa function of the level of coating material within said vessel.

10. Apparatus in accordance with claim 6 wherein said vapor directingmeans is a nozzle within said coating chamber, and means outside of saidcoating chamber for vaporizing the coating material, said last mentionedmeans being in communication with said nozzle and with said vessel.

11. Apparatus in accordance with claim 6 including means outside of saidhousing for vaporizing the coating material, said means for degassingthe coating material being connected to said vaporizing means, amanifold within said coating chamber, a plurality of discharge nozzleson said manifold, and conduit means connecting said vaporizing meanswith said manifold and with said vessel.

12. Apparatus in accordance with claim 6 wherein said degassing means isstructurally interrelated with said vessel to return the degassedcoating material to said vessel.

13. Apparatus comprising a housing having -a coating chamber, means forevacuating said chamber, means within said chamber for'directingvaporized coating material at an element to be coated, a vessel meansoutside of said chamber, means providing fluid communication betweensaid vessel means and vapor directing means, said fluid communicationmeans including means for degassing the coating material before it isintroduced to said vapor directing means, and means for causing thecoating material to ow from the vessel means to the vapor directingmeans.

14. Apparatus in accordance with claim 13 including means for vaporizingthe degassed coating material before it is introduced into the yvapordirecting means.

References Cited UNITED STATES PATENTS 2,621,625 l2/1952 Brown 118-492,909,149 l0/1959 Gerow 117-107 X 3,059,612 10/1962 Baughman et al.117-107 X 3,091,556 5/1963 Behindt et al. 117-107.1 X 3,206,325 9/1965Auerbach ll7-107.l X

ALFRED L. LEAVITI, Primary Examiner.

A. GOLlAN, Assistant Examiner.

